Mauro Giuliani was an Italian guitarist and composer who lived from 1781-1829. He composed a lot of pieces for the guitar ranging from beginner-level pieces all the way up to pieces composed for the concert hall.
In this lesson I will teach you to play his Andantino (Op. 50, No. 1) which I see as an early intermediate level piece.
Anton Diabelli was an Austrian music publisher who also composed music. He is most famous for having composed the waltz that Beethoven used for his Diabelli Variations. Diabelli composed many wonderful pieces for the guitar. This is a perfect piece for the late-beginner guitar student.